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Randomized phase II selection trial of FLASH and conventional radiotherapy for patients with localized cutaneous squamous cell carcinoma or basal cell carcinoma: A study protocol. Clin Transl Radiat Oncol 2024; 45:100743. [PMID: 38362466 PMCID: PMC10867306 DOI: 10.1016/j.ctro.2024.100743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 01/03/2024] [Accepted: 02/03/2024] [Indexed: 02/17/2024] Open
Abstract
Background Cutaneous basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the most prevalent skin cancers in western countries. Surgery is the standard of care for these cancers and conventional external radiotherapy (CONV-RT) with conventional dose rate (0.03-0.06 Gy/sec) represents a good alternative when the patients or tumors are not amenable to surgery but routinely generates skin side effects. Low energy electron FLASH radiotherapy (FLASH-RT) is a new form of radiotherapy exploiting the biological advantage of the FLASH effect, which consists in delivering radiation dose in milliseconds instead of minutes in CONV-RT. In pre-clinical studies, when compared to CONV-RT, FLASH-RT induced a robust, reproducible and remarkable sparing of the normal healthy tissues, while the efficacy on tumors was preserved. In this context, we aim to prospectively evaluate FLASH-RT versus CONV-RT with regards to toxicity and oncological outcome in localized cutaneous BCC and SCC. Methods This is a randomized selection, non-comparative, phase II study of curative FLASH-RT versus CONV-RT in patients with T1-T2 N0 M0 cutaneous BCC and SCC. Patients will be randomly allocated to low energy electron FLASH-RT (dose rate: 220-270 Gy/s) or to CONV-RT arm. Small lesions (T1) will receive a single dose of 22 Gy and large lesions (T2) will receive 30 Gy in 5 fractions of 6 Gy over two weeks.The primary endpoint evaluates safety at 6 weeks after RT through grade ≥ 3 toxicity and efficacy through local control rate at 12 months. Approximately 60 patients in total will be randomized, considering on average 1-2 lesions and a maximum of 3 lesions per patients corresponding to the total of 96 lesions required. FLASH-RT will be performed using the Mobetron® (IntraOp, USA) with high dose rate functionality.LANCE (NCT05724875) is the first randomized trial evaluating FLASH-RT and CONV-RT in a curative setting.
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A Case Report of Metastatic Atypical Thymic Carcinoid with Ectopic ACTH Production: Locoregional Control after Adaptive Radiation Treatment. TUMORI JOURNAL 2018. [DOI: 10.1177/030089161209800632] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Thymic carcinoid is an extremely rare malignancy. This tumor is often associated with endocrine disorders such as Cushing's syndrome, multiple endocrine neoplasia type 1 and superior vena cava syndrome. We describe the case of a 44-year-old Italian woman with metastatic atypical thymic carcinoid secreting ectopic adrenocorticotropic hormone who was treated with adaptive radiation therapy with a curative dose schedule for a symptomatic mediastinal tumor. After 22 months, the patient was in good clinical condition, presenting stable disease without any evidence of local or systemic progression. To our knowledge there are no previously reported data regarding radical radiotherapy in the treatment of thymic carcinoids.
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Ruta chalepensis L. (Rutaceae) leaf extract: chemical composition, antioxidant and hypoglicaemic activities. Nat Prod Res 2017; 32:521-528. [DOI: 10.1080/14786419.2017.1326491] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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4
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EP-1679: A single centre experience of using helical tomotherapy (HT) for craniospinal irradiation (CSI). Radiother Oncol 2016. [DOI: 10.1016/s0167-8140(16)32930-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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5
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Radiation-induced malignant meningioma following proton beam therapy for a choroidal melanoma. J Clin Neurosci 2015; 22:1036-7. [DOI: 10.1016/j.jocn.2014.12.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/18/2014] [Accepted: 12/20/2014] [Indexed: 02/07/2023]
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EP-1181: SBRT in oligometastatic/oligorecurrent NSCLC cancer patients: a new therapeutic approach. Radiother Oncol 2015. [DOI: 10.1016/s0167-8140(15)41173-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Role of salvage stereotactic body radiation therapy in post-surgical loco-regional recurrence in a selected population of non-small cell lung cancer patients. Anticancer Res 2015; 35:1783-1789. [PMID: 25750343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
AIM This is a retrospective analysis of a selected series of high-risk non-small cell lung cancer (NSCLC) patients with post-surgical loco-regional relapse treated with salvage stereotactic body radiotherapy (SBRT). Outcome and toxicity profiles were assessed. PATIENTS AND METHODS Twenty-eight patients (unfit for surgery or systemic therapy) with 30 lesions underwent salvage SBRT as an alternative therapy because of advanced age, co-morbid conditions or no response obtained from other treatments. RESULTS Complete and partial responses were 16% and 70%, respectively. Local progression was observed in 3 patients. Regional relapse occurred in 5 patients. Distant progression occurred in 10 patients. The 2-year overall survival (OS) and disease-free survival (DFS) were 57.5% and 36.6%, respectively. Radiation acute pneumonitis occurred as follows: three patients developed grade 1, two patients experienced grade 2 and one patient experienced grade 3 toxicity. CONCLUSION Stereotactic body radiotherapy could have an alternative role in isolated loco-regional relapse in patients unfit or resistant to other therapies.
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P08.17 * REPEAT STEREOTACTIC RADIOSURGERY (SRS) FOR RECURRENT BRAIN METASTASES. Neuro Oncol 2014. [DOI: 10.1093/neuonc/nou174.205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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P17.57 * COMBINED CHEMORADIATION IN ELDERLY PATIENTS WITH GLIOBLASTOMA: COMPARISON OF TWO RADIATION SCHEDULES. Neuro Oncol 2014. [DOI: 10.1093/neuonc/nou174.386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Neoadjuvant chemoradiation with concomitant boost radiotherapy associated to capecitabine in rectal cancer patients. Int J Colorectal Dis 2014; 29:835-42. [PMID: 24825722 DOI: 10.1007/s00384-014-1879-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/18/2014] [Indexed: 02/04/2023]
Abstract
PURPOSE The primary end-points were complete pathological response and local control. Secondary end-points were survivals, anal sphincter preservation, and toxicity profile. METHODS Patients with T3/T4 and or N+ rectal cancer (n = 65) were treated with preoperative concomitant boost radiotherapy (55 Gy/25 fractions) associated to concurrent chemotherapy with oral capecitabine. RESULTS All patients completed the programmed treatment. The complete pathological response was achieved by 17 % of the patients. Anal sphincter preservation surgery was possible for 86 % of the patients with low rectal cancer (≤ 5 cm from the anal verge). The T-stage and N-stage downstaging were achieved by 40 and 58 % of the patients, respectively. Circumferential radial margin was involved (close/positive) in eight patients. After a median follow-up of 26 months, local and distant recurrence occurred in two and 11 patients, respectively. The 3-year overall survival and disease-free survival were 86.8 and 81 %, respectively. Non-hematological ≥ grade 3 toxicities were observed in 15 % of the patients. On univariate analysis N-downstaging and positive circumferential radial margin were significantly associated with worse overall survival (p = 0.003 and p = 0.023, respectively), disease-free survival (p = 0.001 and p = 0.036, respectively), and metastasis-free survival (MFS) (p = 0.001 and p = 0.038, respectively).On multivariate analysis, the N-downstaging were significantly associated with better overall survival (OS) (p = 0.022). CONCLUSIONS Our data support the efficacy of preoperative treatment for rectal cancer in terms of local outcomes. Radiation treatment intensification may have a biological rationale; longer follow-up is needed.
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Fractionated stereotactic radiosurgery for patients with skull base metastases from systemic cancer involving the anterior visual pathway. Radiat Oncol 2014; 9:110. [PMID: 24886280 PMCID: PMC4036429 DOI: 10.1186/1748-717x-9-110] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 03/16/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To analyze the tumor control, survival outcomes, and toxicity after stereotactic radiosurgery (SRS) for skull base metastases from systemic cancer involving the anterior visual pathway. PATIENTS AND METHODS We have analyzed 34 patients (23 females and 11 males, median age 59 years) who underwent multi-fraction SRS for a skull base metastasis compressing or in close proximity of optic nerves and chiasm. All metastases were treated with frameless LINAC-based multi-fraction SRS in 5 daily fractions of 5 Gy each. Local control, distant failure, and overall survival were estimated using the Kaplan-Meier method calculated from the time of SRS. Prognostic variables were assessed using log-rank and Cox regression analyses. RESULTS At a median follow-up of 13 months (range, 2-36.5 months), twenty-five patients had died and 9 were alive. The 1-year and 2-year local control rates were 89% and 72%, and respective actuarial survival rates were 63% and 30%. Four patients recurred with a median time to progression of 12 months (range, 6-27 months), and 17 patients had new brain metastases at distant brain sites. The 1-year and 2-year distant failure rates were 50% and 77%, respectively. On multivariate analysis, a Karnofsky performance status (KPS) >70 and the absence of extracranial metastases were prognostic factors associated with lower distant failure rates and longer survival. After multi-fraction SRS, 15 (51%) out of 29 patients had a clinical improvement of their preexisting cranial deficits. No patients developed radiation-induced optic neuropathy during the follow-up. CONCLUSIONS Multi-fraction SRS (5 x 5 Gy) is a safe treatment option associated with good local control and improved cranial nerve symptoms for patients with a skull base metastasis involving the anterior visual pathway.
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Intermediate-risk prostate cancer patients treated with androgen deprivation therapy and a hypofractionated radiation regimen with or without image guided radiotherapy. Radiat Oncol 2013; 8:137. [PMID: 23759081 PMCID: PMC3691824 DOI: 10.1186/1748-717x-8-137] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 06/01/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To evaluate the efficacy of hypofractionated radiotherapy (HyRT) with or without image guided radiotherapy (IGRT) in intermediate risk prostate cancer. METHODS 105 patients were treated with HyRT, 43,8 Gy and 54,75 Gy were delivered to the seminal vescicles and to the prostate, respectively; 3,65 Gy/fraction three times weekly. All patients underwent 9 months hormonal therapy. Patient position was verified with daily kV cone beam CT in 69 patients (IGRT group). Acute and late toxicities were evaluated according to RTOG scale. Biochemical relapse was defined using PSA nadir + 2 ng/mL. The data were prospectively collected and retrospectively analyzed to evaluate the efficacy of IGRT. RESULTS After a median follow-up of 31 months the actuarial 3-year bNED was 93,7%. During RT, 10.5% and 7.6% of patients developed ≥Grade 2 rectal and urinary toxicities, respectively. The cumulative incidence of ≥Grade 2 late rectal and urinary toxicities at 3 years were 6,9%, and 10,8%, respectively. The incidence of ≥Grade 2 late rectal toxicities was significant reduced in the IGRT group (1,6% vs. 14,5%, p=0,021). Two patients developed Grade 3 urethral obstruction and one patient developed grade 3 rectal bleeding. CONCLUSIONS HyRT represents a well-tolerated treatment able to achieve a high bNED. The use of daily IGRT is beneficial for reducing the incidence of late toxicities.
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A case report of metastatic atypical thymic carcinoid with ectopic ACTH production: locoregional control after adaptive radiation treatment. TUMORI JOURNAL 2013; 98:172e-5e. [PMID: 23389379 DOI: 10.1700/1217.13516] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Thymic carcinoid is an extremely rare malignancy. This tumor is often associated with endocrine disorders such as Cushing's syndrome, multiple endocrine neoplasia type 1 and superior vena cava syndrome. We describe the case of a 44-year-old Italian woman with metastatic atypical thymic carcinoid secreting ectopic adrenocorticotropic hormone who was treated with adaptive radiation therapy with a curative dose schedule for a symptomatic mediastinal tumor. After 22 months, the patient was in good clinical condition, presenting stable disease without any evidence of local or systemic progression. To our knowledge there are no previously reported data regarding radical radiotherapy in the treatment of thymic carcinoids.
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Image guided hypofractionated 3-dimensional radiation therapy in patients with inoperable advanced stage non-small cell lung cancer. Int J Radiat Oncol Biol Phys 2012. [PMID: 23182393 DOI: 10.1016/j.ijrobp.2012.10.012] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE Hypofractionated radiation therapy (HypoRT) can potentially improve local control with a higher biological effect and shorter overall treatment time. Response, local control, toxicity rates, and survival rates were evaluated in patients affected by inoperable advanced stage non-small cell lung cancer (NSCLC) who received HypoRT. METHODS AND MATERIALS Thirty patients with advanced NSCLC were enrolled; 27% had stage IIIA, 50% had stage IIIB, and 23% had stage IV disease. All patients underwent HypoRT with a prescribed total dose of 60 Gy in 20 fractions of 3 Gy each. Radiation treatment was delivered using an image guided radiation therapy technique to verify correct position. Toxicities were graded according to Radiation Therapy Oncology Group morbidity score. Survival rates were estimated using the Kaplan-Meier method. RESULTS The median follow-up was 13 months (range, 4-56 months). All patients completed radiation therapy and received the total dose of 60 Gy to the primary tumor and positive lymph nodes. The overall response rate after radiation therapy was 83% (3 patients with complete response and 22 patients with partial response). The 2-year overall survival and progression-free survival rates were 38.1% and 36%, respectively. Locoregional recurrence/persistence occurred in 11 (37%) patients. Distant metastasis occurred in 17 (57%) patients. Acute toxicities occurred consisting of grade 1 to 2 hematological toxicity in 5 patients (17%) and grade 3 in 1 patient; grade 1 to 2 esophagitis in 12 patients (40%) and grade 3 in 1 patient; and grade 1 to 2 pneumonitis in 6 patients (20%) and grade 3 in 2 patients (7%). Thirty-three percent of patients developed grade 1 to 2 late toxicities. Only 3 patients developed grade 3 late adverse effects: esophagitis in 1 patient and pneumonitis in 2 patients. CONCLUSIONS Hypofractionated curative radiation therapy is a feasible and well-tolerated treatment for patients with locally advanced NSCLC. Randomized studies are needed to compare HypoRT to conventional treatment.
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Adrenergic effects on force-frequency relationship: a pivotal role for the cardiac intrinsic systems. Acta Physiol (Oxf) 2011; 202:141-9. [PMID: 21338472 DOI: 10.1111/j.1748-1716.2011.02266.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM The force-frequency relationship (F-FR) is an important intrinsic regulatory mechanism of cardiac contractility. The involvement of autonomic nervous system in this physiological aspect of cardiac control remains unclear. The aim of the study was to evaluate the role of extrinsic and intrinsic cardiac adrenergic innervations on the heart rate (HR)-related positive inotropic response. METHODS Twenty-four dogs were anesthetized and acutely instrumented to monitor and record ECG, systemic and left ventricular pressures and derivatives, and to pace the heart at 130, 150, 170, 190 and 210 bpm, in order to construct the F-FR curve. Animals were randomly assigned to four groups (n = 6 each): vehicle (V), ganglion-blocked (G-B), β-blocked (β-B) and ganglion-blocked plus β-blocked (G-B + β-B). RESULTS Vehicle treated animals presented the classical F-FR. In the β-B group F-FR was blunted, but never fully suppressed. The G-B treated animals showed a bell-shape response curve of the induced inotropic effect with the zenith at 170 bpm: the first part of the curve resembling the control one, followed by a rapid decline toward baseline value. The co-administration of G-B and β-B agents reversed the contractile response to HR rise with a curve resembling the negative F-FR curve observed in the failing heart. CONCLUSION The F-FR appeared to be constituted by two consecutive mechanisms: first depolarization-rate dependent, and a second catecholamine-dependent. The natural consequence of these observations is that the full expression of F-FR needs an intact adrenergic system.
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WE-D-220-05: Development of Autoscanning 3D Ultrasound Technology for Radiotherapy Simulation, Planning and IGRT. Med Phys 2011. [DOI: 10.1118/1.3613359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Fractal analysis reveals reduced complexity of retinal vessels in CADASIL. PLoS One 2011; 6:e19150. [PMID: 21556373 PMCID: PMC3083432 DOI: 10.1371/journal.pone.0019150] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 03/18/2011] [Indexed: 01/23/2023] Open
Abstract
The Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) affects mainly small cerebral arteries and leads to disability and dementia. The relationship between clinical expression of the disease and progression of the microvessel pathology is, however, uncertain as we lack tools for imaging brain vessels in vivo. Ophthalmoscopy is regarded as a window into the cerebral microcirculation. In this study we carried out an ophthalmoscopic examination in subjects with CADASIL. Specifically, we performed fractal analysis of digital retinal photographs. Data are expressed as mean fractal dimension (mean-D), a parameter that reflects complexity of the retinal vessel branching. Ten subjects with genetically confirmed diagnosis of CADASIL and 10 sex and age-matched control subjects were enrolled. Fractal analysis of retinal digital images was performed by means of a computer-based program, and the data expressed as mean-D. Brain MRI lesion volume in FLAIR and T1-weighted images was assessed using MIPAV software. Paired t-test was used to disclose differences in mean-D between CADASIL and control groups. Spearman rank analysis was performed to evaluate potential associations between mean-D values and both disease duration and disease severity, the latter expressed as brain MRI lesion volumes, in the subjects with CADASIL. The results showed that mean-D value of patients (1.42±0.05; mean±SD) was lower than control (1.50±0.04; p = 0.002). Mean-D did not correlate with disease duration nor with MRI lesion volumes of the subjects with CADASIL. The findings suggest that fractal analysis is a sensitive tool to assess changes of retinal vessel branching, likely reflecting early brain microvessel alterations, in CADASIL patients.
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SU-GG-J-23: Accurate Dose Assessment for Prostate Cancer Patients Using 3D Ultrasound and Monte Carlo Dose Calculation. Med Phys 2008. [DOI: 10.1118/1.2961580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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SU-FF-J-67: Monte Carlo Dose Calculation in Prostate Patients Aided by 3D Ultrasound Imaging. Med Phys 2005. [DOI: 10.1118/1.1997613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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TH-C-I-609-04: A Quick and Accurate Calibration Method for 3D Ultrasound in Image-Guided Radiotherapy. Med Phys 2005. [DOI: 10.1118/1.1998629] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Comparison of bat system and a new 3D trans-abdominal ultrasound-based image-guided system for prostate daily localization during external beam radiotherapy. Int J Radiat Oncol Biol Phys 2004. [DOI: 10.1016/j.ijrobp.2004.07.150] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Elimination of ghost markers during dual sensor-based infrared tracking of multiple individual reflective markers. Med Phys 2004; 31:2008-19. [PMID: 15305453 DOI: 10.1118/1.1760186] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The accuracy of dose delivery in radiotherapy is affected by the uncertainty in tumor localization. Motion of internal anatomy due to physiological processes such as respiration may lead to significant displacements which compromise tumor coverage and generate irradiation of healthy tissue. Real-time tracking with infrared-based systems is often used for tracking thoracic motion in radiation therapy. We studied the origin of ghost markers ("crosstalk") which may appear during dual sensor-based infrared tracking of independent reflective markers. Ghost markers occur when two or more reflective markers are coplanar with each other and with the sensors of the two camera-based infrared tracking system. Analysis shows that sensors are not points but they have a finite extent and this extent determines for each marker a "ghost volume." If one reflective marker enters the ghost volume of another marker, ghost markers will be reported by the tracking system; if the reflective markers belong to a surface their "ghost volume" is reduced to a "ghost surface" (ghost zone). Appearance of ghost markers is predicted for markers taped on the torso of an anthropomorphic phantom. This study illustrates the dependence of the shape, extent, and location of the ghost zones on the shape of the anthropomorphic phantom, the angle of view of the tracking system, and the distance between the tracking system and the anthropomorphic phantom. It is concluded that the appearance of ghost markers can be avoided by positioning the markers outside the ghost zones of the other markers. However, if this is not possible and the initial marker configuration is ghost marker-free, ghost markers can be eliminated during real-time tracking by virtue of the fact that they appear in the coordinate data sequence only temporarily.
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Abstract
Ultrasound (US) image-guided patient positional verification was performed daily on four prostate cancer patients using the BAT system (NOMOS Corporation, CA). The BAT system has shown that the prostate can shift by as much as 1 cm from its intended position in any direction. Furthermore, the daily shifts measured by the BAT system were included into the treatment planning system to assess changes in prostate dose coverage. Dose volume histograms were used to compare the dosimetry between the ideal patient set-up situation (prostate always positioned correctly) and that taking all patient daily shifts into consideration. Daily patient shifts on the order of magnitudes measured, can significantly and adversely affect dosimetric coverage, therefore an US-based patient positioning system is required for improving the therapeutic ratio.
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Abstract
A semi-automatic technique for the direct setup alignment of radiosurgical circular fields from an isocentric linac to treatment room laser cross-hairs is described. Alignment is achieved by acquiring images of the treatment room positioning laser cross-hairs superimposed on the radiosurgical circular field image. An alignment algorithm calculates the center of the radiosurgical field image as well as the intersection of the laser cross-hairs. This determines any alignment deviations and the information is then used to translate the radiosurgical collimator to its correct aligned position. Two detectors, each being sensitive to the lasers and ionizing radiation, were used to acquire the radiation/laser images. The first detector consists of a 0.3-mm-thick layer of photoconducting a-Se deposited on a 1.5-mm-thick copper plate and the second is film. The algorithm and detector system can detect deviations with a precision of approximately 0.04 mm. A device with gyroscopic degrees of freedom was built in order to firmly hold the detector at any orientation perpendicular to the radiosurgical beam axis. This device was used in conjunction with our alignment algorithm to quantify the isocentric sphere relative to the treatment room lasers over all gantry and couch angles used in dynamic stereotactic radiosurgery.
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Characteristics of metal-plate/film detectors at therapy energies. II. Detective quantum efficiency. Med Phys 1998; 25:2463-8. [PMID: 9874840 DOI: 10.1118/1.598437] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Noise power spectrum (NPS) and detective quantum efficiency (DQE) for metal-plate/film portal detectors are reported for the Co-60 and Linac 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of aluminum, copper, brass, or lead. The NPS was found to be independent of the detector sensitivity demonstrating that the film grain noise dominates over the quantum noise. Although the detector signal increases with density of the backplates, the resultant electron-backscatter increases detector blur, thus decreasing the DQE. The lowest DQEs are therefore produced with the lead backplates, irrespective of the front plates. For a given backplate and for front-plate thicknesses less than the maximum electron range, the DQE increases with density of the front plate.
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Characteristics of metal-plate/film detectors at therapy energies. I. Modulation transfer function. Med Phys 1998; 25:2455-62. [PMID: 9874839 DOI: 10.1118/1.598436] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Measurements of modulation transfer function (MTF) for front and back metal-plate/film portal detectors are reported for the Cobalt-60 and 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of Al, Cu, brass, or Pb with thicknesses varying from 0 to 4.81 mm. Secondary electrons produced within the front plate generate the main signal, but the MTF decreases with an increase in front plate thickness greater than the maximum range of electrons Rmax because of photon scatter in the front plate. Because the decrease of MTF with backplate thickness ceases for backplate thickness greater than Rmax, the MTF is influenced more by the backscatter electrons than the backscatter photons.
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Abstract
A feasibility study has been performed on metal/amorphous selenium detectors for megavoltage portal imaging. The metal plates of the detectors were positioned facing the incident 6 MV and Co-60 photon spectra. The detectors consist of various thicknesses (0.15 mm, 0.30 mm, and 0.50 mm) of amorphous selenium (a-Se) deposited on metal plates of varying thicknesses: aluminum (2.0 mm), copper (1.0 mm and 1.5 mm), stainless steel (0.9 mm), or glass (1.1 mm). The detectors were charged prior to irradiation by corona methods, and the portal images were subsequently digitized after irradiation with a noncontact electrostatic probe. The sensitivity of the detectors to dose, electric field across the a-Se layer, metal plate type and a-Se thickness, was studied. The electrostatic voltage remaining on the a-Se layer was found, both theoretically and experimentally, to exhibit a cubic relationship with respect to dose. An increase in electric field increases the sensitivity (gradient of the a-Se surface voltage vs dose curve) and dynamic range of the resultant image. An increase in a-Se thickness, however, although also increasing the sensitivity, decreases the dynamic range. The metal plate types and thicknesses within the range studied do not have a significant effect on detector sensitivity. Image quality and contrast resolution of the detector were evaluated with a contrast-detail phantom and compared to commercially available film based and electronic portal imaging devices. Image quality of the metal/a-Se detector as a function of dose was studied by discharging the a-Se to various fractions of its initial charge, and as expected, increases with dose due to a decrease in quantum noise. Contrast-detail images obtained by metal/a-Se detectors are superior to those obtained at higher dose levels by other commercial systems.
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